1. Field of the Invention
The present invention relates to an electroluminescence (EL) device, in particular, an improvement in moisture and gas resistance.
The present invention also relates to a method for manufacturing such an EL device.
2. Description of the Related Art
Up to now, EL devices, for example, inorganic or organic EL devices have been widely put into practical use as displays for thin, lightweight portable devices or illuminators on account of being self-luminous and capable of providing a high-luminance screen. The EL device has a structure in which an EL element is formed on a substrate, the EL element having a pair of electrode layers, at least one of which constitutes a transparent electrode, and a light emitting layer interposed between the electrode layers.
As regards this type of EL device, there is a possibility that the light emitting layer or the electrode layer of the EL element is damaged by intrusion of oxygen or other gases, moisture, etc. to deteriorate an image quality or shorten a lifetime. To cope with this, it has been proposed to cover the surface of the EL element with a protective film for avoiding the intrusion of oxygen or other gases, moisture, etc. from the outside.
For example, JP 2002-222691 A discloses a technique for applying polysilazane to the surface of an EL element to form a silica film or silica-based film as a protective film. In addition, JP 3170542 B discloses an organic EL element on the surface of which an inorganic amorphous film selected from the group consisting of an α-Si film, an α-SiC film, an α-SiN film, and an α-C film is formed as a protective film by plasma CVD and the like methods.
Further, JP 2003-118030 A discloses an EL device prepared by forming a gas barrier layer on the surface of an organic base material through a dry process and in addition, forming a cured substance layer made of a cured substance of a polysilazane-containing composition on the surface of the gas barrier layer through a wet process, and arranging the base material on the surface of the EL element.
However, if aiming at directly applying polysilazane onto the surface of the EL element to form a silica film etc. as proposed in JP 2002-222691 A, an electrode layer or light emitting layer of the EL element is in danger of being damaged by a solvent in the applied polysilazane solution. In the case of forming a film by plasma CVD etc. as proposed in JP 3170542 B, the film formed through the plasma CVD is limited of its throwing power. For example, if foreign matters exist on the surface of the EL element, the foreign matters cannot be completely covered with an inorganic amorphous film and uncovered portions may allow the intrusion of oxygen or other gases, moisture, etc. Such intrusion of oxygen or other gases, moisture, etc. in the EL element induces deterioration of the light emitting layer, causing dark spots that may grow as time goes by.
Further, assuming that the gas barrier layer and the cured substance layer are formed on the surface of the organic base material and the base material is arranged on the surface of the EL element as proposed in JP 2003-118030 A, the following problems arise. That is, the above arrangement complicates a structure of the EL device with a larger thickness as well as a manufacturing process therefor.